Evolving from Batch to Continuous Production of Extrusion...

Evolving from Batch to

Continuous Production of

Sealants Using Twin Screw

Extrusion Technology

Dhruv Lad.

Sales Engineer Chemical Applications

Coperion Corporation – Pitman, NJ

Batch to Continuous for Sealant Production

Agenda


I. Discontinuous Sealant productions

II. Continuous Sealant production

III. Comparison & conclusion

Discontinuous Sealant production

• Batch kneader with discharge screw

• Blades according to process requirements

• Possibility to attach downstream equipment

• Middle- to high viscous hot melt

• Variant for low viscous hot melts: kneader with

bottom valve for emptying in intermediate vessels


Planetary mixers

• Double planetary mixer with combined agitators

• Rotating on their own axes as they orbit on a

common axis

• Various agitators useable

• Convertible agitators

• Mobile mixing vessel for transport

Masticator blade

Sigma- / Z- blade

Rectangular blade

High viscosity (HV) blade

Coperion Werner & Pfleiderer UK-A

Source: Charles Ross & Son Company

Discontinuous Sealant production –Work routine


Weighing of the raw materials

Addition and plasticisation/ mastication of the

base polymers

Addition of fillers (if existent)

Addition of a subset of low-viscous and

low-melting resins, waxes

Addition of residual amount of low-viscous

and low-melting resins, waxes

Addition of softeners (if existent)

Addition of additives

Degassing

Discharging

Cleaning at recipe- or colour changes

Vis

co

sity d

ecre

ase

Discontinuous Sealant production –Requirements and limiting characteristics


Limiting characteristics

• Increased personnel expenses

• Long processing times

• Big cyclic cleaning effort

• Batch quality variations

• Degassing difficulty

Requirements for production technology

• Flexibility

• Economics

• Efficiency

Competitiveness correlates with the characteristics of the limiting factors of a

production technology.

Continuous production machines


+ ++ + + +

co-rotating counter-rotating

intermeshing tangential

+ +

Single screw

extruderCo-Kneader

Twin screw extruderSingle screw extruder Multiple screw extruder

Ring-

extruder

Planetary

extruder

Comparison of continuous extrusion systems


Feed intake of bulk materials

Downstream adding of liquids

Melting capability of

In axial direction

Crosswise

Dispersive mixing

Degassing capability

Pressure build-up capability

Self cleaning

Residence time distribution

Modular design of

Possibility of heating and/or

cooling of

++

+ +

++

++

+++

+++ +++

++++++

++++++

+ +

+

+

+

+

+ +

++

+++++ +++

+++

+++

+++

+++

+++ +++

++++++

++++++

++ ++ + ++ + + ++ + + ++ +

Powder

Pellets

Screws

Barrels

Screws

Barrels

Single screw exruder

Single screw Co-Kneader

Twin screw extruderCo-rotating Counter-rotating

Intermeshing Tangential

Multiple screw extruderPlanetary

extruderRingextruder

+

+

+

+

++

++

++

++

++

++

no

wide

no

no

yes

yes

++

+++

+++

++

+++

+++

+++

++

+

+

yes

narrow

yes

yes

yes

yes

+++

+++

++

+++

+++

+++

+++

+++

+++

+

yes

narrow

yes

yes

yes

yes

+++

+

+

++

++

+

+

++

+

+++

yes

very narrow

no

yes

yes

yes

++

-

+

+++

+

+++

+++

++

-

-

no

wide

no

no

yes

yes

++

-

+

++

++

++

++

+++

++

+

in the planets only

narrow

yes

yes

yes

yes

+++

+++

++

+++

+++

+++

++

+++

+++

+

yes

narrow

yes

yes

yes

yes

Extruder systems

Characteristics

Distributive mixing

Screw

paddel

- Hub+ Hub

Rotation

Kneading

pin

Downstream adding of bulk materials

Twin Screw History


Market introduction of the first co-rotating twin screw extruder (ZSK 83) in 1957

Continuous production of Sealant –Modular design


Modular design for screw elements and kneading blocks

Operating principle

Motor Gear box Processing section

Intermeshing screw profile

ZSK 125 MEGAvolume PLUS

Conveying,

Side feeding

Mixing

Kneading

Fillers and

resin

Polymer,

rubber

FeedingMelting,

MasticationVenting

Homogeni-

zation

Vacuum

degassing

DegassingMetering,

Discharge

Atmospheric

venting

Liquid resins and plasticizers

Continuous production of Sealant –Process section of a co-rotating twin screw extruder


Continuous production of Sealant –Components


Material Handling

Raw material silo

Big Bag unloading station

Bag unloading station

Feeding Equipment

Liquid feeders

Loss-in-Weight feeders (powder/pellets)

Discharge Equipment

Direct filling

Silicone Sealants


1 Extruder ZSK

2 Silicone Polymer feeder

3 Aerosil feeder

4 Cross linker feeder

5 Silicon-Oil feeder

6 Catalyst feeder

7 Vacuum system

8 Discharge Equipment

RTV Silicon - Sealant


1 Grav. feeder Aerosil 5 Grav. feeder Catalyst 9 Start up valve

2 Grav. feeder Silicon-Pol. 6 Extruder ZSK

3 Grav. feeder Silicon-Oil 7 Maindrive and gearbox

4 Grav. feeder Crosslinker 8 Vacuum

Continuous production of Sealant–Working principle


• Workflow continuously, regardless of product and batch size

• Automatic start-up and shutdown of the plant

• Automatic and gravimetrically controlled dosing of raw materials

• Intake, Conveying, melting, mixing, homogenizing and degassing

• Filtering and transport to downstream equipment

FET:

Technology to increase the throughput

of feed limited products

Solids conveying is improved by

applying vacuum in the feed zone to

a wall section which is porous and

permeable to gas.

FET- Feed Enhancement Technology


Effects:

• air is removed higher bulk density

• friction is changed in the area of insert

Vacuum

Filter cake: densified powderFET insertAir

FET: working principle


• Temperature/ time- stress decisive for achieved product quality

• Kneading time vs. temperature peaks and sheer speeds

• Integral value (product damage) drastically reduced in continuous process

Continuous production of Sealant–Temperature control


Continuous production of Sealant–Cleaning and recipe change


• Self cleaning (intermeshing) screw profile

• Recipe changes possible within a few minutes

• Use of cleaning media and cleaning devices

Continuous production of Sealant–Process advantages


• Optimal product intake

• Wide viscosity range (up to 100.000.000 mPas)

• Very good mixing quality

• High degassing efficiency

• Set-up time reduction by self cleaning screw profile

• Short thermal stress

• High degree of automation at low personnel expenses

• Reproducibility and proof of quality by process data storage

• Modular, highly flexible system

Continuous vs. discontinuous production of Sealant–Comparison


Criteria Discontinuous kneader 900l

with discharge screw

Continuous Extruder ZSK 54Mv

Twin- screw 54mm Ø

Throughput (kg/h) 600 600

Energy intake mostly thermal conduction mostly dissipation

Typical shear rate range (sec-1) < 200 < 1800

Residence time (min) in melt phase

(thermal stress)60 -120 1 - 2

Self cleaning poor very good

Cleaning effort at recipe change high low

Space requirement (m²) ca. 150 ca. 180

Personnel needs 2 - 3 1 - 2

Quality varies per batch consistent

Investment 100% 150%

Conclusion


• A technical comparison between a discontinuous and a continuous plant is particularly led in regards of

feeding, recipe changes, cleaning, thermal stress of the melt (degradation), personnel costs and quality

consistency.

• The continuous production relies on the accuracy of feeding raw materials to the extruder. Complex systems

enable the production of formulations with many different raw materials as well as frequent recipe changes.

• Due to the self-cleaning properties of the extruder, color and/or filler changes can be realized within less than

half an hour. The new product cleans the process part in a very short time and purges the remaining

residuals of the previous formulation. The amount of produced off-spec material is decreased tremendously.

• The thermal and oxidative degradation of the adhesive is limited due to the virtually closed system of the

extruder (no oxygen in N2 overlay) and the very short residence time (in the range of 1 min) extremely low.

• Sealant validation of quality consistency is mainly dependent on the feeding accuracy. Deviations of the

gravimetric feeders are reported and documented by leading edge control concepts which allows for purging

of off-spec material by a bypass until the quality is back on spec.

• Additional process quality parameters are screw torque, screw speed, temperature (melt & barrel steel), and

pressure (melt, inlet, & discharge).

• The positives of discontinuous processing include small batches, very complex recipes and for raw materials

which are not flowable.

• Economically, a continuous system is the right decision due to: consistent high quality, reproducibility,

minimal setup & start-up time, and the high degree of automation at reduced personnel expenses.

Thank you for your attention!

Evolving from Batch to Continuous Production of Extrusion...

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